On 21/01/2013 pecheur wrote:>M9 firstly no one your age is allowed to use the phrase dissing ;)>
The term was around before you were born whippersnapper!
... and some time in the future you will be older too!! ~> What contemporary jargon will you diss using?
Heh, heh, heh.

>Secondly I agree that misinformation shouldn't be on the web. Whether>it's life threatening is a different question. Given it grossly overestimates>loads I'd be too scared at all to climb with those sorts of forces 1 metre>out from my last piece of gear :P

This assumes some sort of understanding of what is involved. I would hazard a guess that for many new climbers in the game, they assume that trad gear and techniques work well in all situations, if in fact they ever use such...
;-)

Post-edited this in my last post but as people are being quick on the draw, here it is again.

FWIT it is possible to have a fall factor greater than 2. This could happen if the belayer has time, say in a 10m fall onto the belay, to take in some slack. So, instead of 10m fall onto 5m of rope, 9.5m fall onto 4.5m of rope would give FF 2.11and 9m fall onto 4m rope give FF2.25. This would probably qualify as a bad thing.

I also can’t understand why you wouldn’t be able to get a fall factor above 2 – in fact that is what looseness in a belay can do for you.

As an example, consider a climber 2m above the belayer who is tied tightly to the belay. The climber falls off, falling 4m then the rope goes tight after a 4m fall. FF= 4/2 = 2 (assuming no slip no elongation & no further slack in the system). This means the force to be counteracted is mass x g x 2 = 16kN for an 80 kg climber. Not a lot of gear holds up that well.

Now consider the climber 2m above the belayer who is tied on but with 1m slack between the belay and the belayer. The climber falls off, falling 4m, then pulling the belayer off and down 1 m, then the rope goes tight after what is now a 5m fall. FF= 5/2 = 2.5 (assuming no slip no elongation & no further slack in the system). This means the force to be counteracted (by the rope) is mass x g x 2.5 = 20kN for an 80 kg climber, plus the weight of the belayer…. Even less likely the gear will hold, especially a less than perfect placement in weakish rock.

Implications:
put in a bombproof belay
and
tie in tight
and…
put in a runner

If the leader put in a runner at 1m, belayer kept everything tight, the fall would have been 2m on 2m of rope out or FF 1 (again, assuming no slip no elongation & no further slack in the system) – a huge reduction in force even with such a short amount of rope out.

Sorry jrc but most of the explanations were pretty bullshit. I'm on my phone so I'll wait till I'm on my computer before I'll explain exactly why. Try looking at the Wikipedia article to realise your oversimplifications are wrong and not even a good approximation. Specifically look at the impact force and how complicated that is.

>As an example, consider a climber 2m above the belayer who is tied tightly>to the belay. The climber falls off, falling 4m then the rope goes tight>after a 4m fall. FF= 4/2 = 2 (assuming no slip no elongation & no further>slack in the system). This means the force to be counteracted is mass x>g x 2 = 16kN for an 80 kg climber. Not a lot of gear holds up that well.>>>Now consider the climber 2m above the belayer who is tied on but with>1m slack between the belay and the belayer. The climber falls off, falling>4m, then pulling the belayer off and down 1 m, then the rope goes tight>after what is now a 5m fall. FF= 5/2 = 2.5 (assuming no slip no elongation>& no further slack in the system). This means the force to be counteracted>(by the rope) is mass x g x 2.5 = 20kN for an 80 kg climber, plus the weight>of the belayer…. Even less likely the gear will hold, especially a less>than perfect placement in weakish rock. >
?!?!?! Somebody with more patience than I please stop me from going ODH on this guy? I'm sure he means to help. Please? That's some of the worst set of assumptions and pseudo physics I've seen.

I apologise about the assumptions comment if jrc climbs with steel cable...

On 21/01/2013 jrc wrote:>I also can’t understand why you wouldn’t be able to get a fall factor above>2 – in fact that is what looseness in a belay can do for you.

Technically looseness in the belay can increase the fall factor but only under very specific and unusual (read retarded) conditions. I'm going to skip over the fact you use the formula Fimpact = mgF. I have no idea where you got this from and it is retarded. For a better approximation check this discussion on Mountain Project and also this article on Beals website.

Back to the looseness of the belay. In your scenario the belayer is clipped into the belay with a certain amount of slack which is then added to the fall length when the leader falls. You posit that this increases the fall factor. This is correct, in the manner in which you explained, if and only if the belayer was connected to the belay using a static method; if the belayer is connected using the rope then this would actually reduce the fall factor.

So if the belayer was connected with a static sling to the belay then it is most likely via a single length sling (0.6m) then it might be possible to get a FF of 2.2 with a 6.6m fall (6m till the belayer is pulled, then the extra 0.6m of slack) from 3m above the belay. However, this is really quite unlikely, as the person would have to having sex with the strong point of the anchor. Really the amount of slack would be much smaller - a conservative estimation would be half that amount in slack, resulting in a FF of 2.1 which in the real world is lost in the noise of other factors not accounted for in this over simplification.

Lets look further though - what if the numpty belayer were tied in with a double length sling. This gives the belayer a whole 1.2m of slack to play around with. Imagining this scenario now I cant think of why the belayer would have this much freedom except if they were on a ledge large enough to walk around on, if this was the case then there most likely wont be a clean fall, the leader will be hitting things on the way down. Fall factors are pointless here because the force generated in the fall isn't the problem (the climber is slowed by hitting things), its the climber hitting things that's the problem.

What about if the belayer had originally extended himself a few metres from the belay to bring up the seconder (soon to be leader, and, it seems, soon to be hurting himself) and then didn't readjust the lanyard but did reposition himself, before the leader started leading? The only reasonable way the belay can extend their belay by that much is with the rope which would reduce the fall factor - the equation would become FF = (Lfall + Lslack) / (Lrope + Lslack). Whatever the length of the fall is the addition of some slack would reduce to the fall factor to below 2.

The only scenario I can envisage of getting a decent increase in the fall factor above 2 would be if there was a belay on a reasonable size ledge (where the belayer could walk around and attach himself in with a double length sling) and the next pitch go out some sort of roof above head height (otherwise the belayer wouldn't be walking around) or traversing off over the end of the ledge (more likely). If the belayer can't see the problem of having slack in the system in this situation (even if the climber clips some pro before he falls the belayer is going to be pulled sideways) then I would be worried about a hell of a lot more than having a fall factor 2 fall. In a FF 2 fall both the belayer and climber are going to be in much pain in this situation.

Thanks also for the wikipedia reference where i found i did at least get the FF calc correct; and as P noted, the elongation of the rope is not relevant as the FF is the pre stress calculation.

As i indicated in my note, my force calculations were an approximation, i admit, for simplicity, and were given primarily for relative purposes but also to show there are severe forces able to be generated even in 'small' falls.

Re the force calc; the energy in the fall would be mgh, this energy being absorbed by the stretching rope and resulting in a force along the distance it stretched,(which would be proportional to the length of rope deployed, not the length of rope itself (as i wrongly calculated giving rise to the mgh / r calc where it should have been mgh / (r x%elongation) (assuming linear elongation in the foregoing)-sorry for the confusion).

With the scenario of the slack in the belay i was trying to see if there was a way you could get the FF above 2 which i always thought was some sort of sensible limit. I did not assume rational belayer behaviour - ie yes he could sit there with a metre of slack in the system and yes i agree that is dumb. Thanks for picking that up

Happy to discuss further ! I'll be in the bar of the Imperial at 6pm on Sunday 27th.

I stated that you couldn't get a fall factor above 2, however I have been corrected by the very unlikely scenario that the belayer is taking in as you are falling!!! If this were the case, then, yes, you might get slightly over FF2.

If the belayer has slackness in the rope, then as someone else has mentioned, this reduces the fall factor and the forces involved. Tightness in the rope results in greater forces albeit the climber falls less of a distance.

Someone discussed the possibility of the belayer having slackness between them and the anchor such that in a fall, the belayer themself was moved. Whilst technically you could say this is a greater than a fall factor 2, just remember why we as climbers talk about FF2's, its to understand the forces involved due to the deceleration of the climber. In the scenario where the belayer is moved this actually bleeds off energy from the fall, decelerating your climber. Energy is conserved in the system, and your belayer is consuming your fall energy (through the violent movement towards the edge of the ledge) that would otherwise have been absorbed by your anchors/rope etc.

The calculation made before equating MGH to a force was wrong, this calculates gravitational potential energy. To calculate force you need to know the distance over which deceleration occurred (indicative by rope stretch).

If you have a nice new rope that has 30% stretch, the force is reduced to 3.3kN.

From above you can see that if the belayer was to be moved by the supposed greater than FF2 due to a slackness between belayer and anchor, then this increases the deceleration distance and reduces the forces involved.

If as I suspect I am wrong about uniform deceleration (ropes don't bounce like a bunjy jump), then the force will be significantly higher then the examples above (at a guess, 50% higher?), however the above is useful for comparing different fall types, etc.

I'm sure we all remember the scene in Young Einstein where Albert is trying to explain relativity.

Q: "If I'm on a train travelling at the speed of light, and I move from the rear carriage to the front carriage, I would be travelling faster than the speed of light."
A: "No you wouldn't, because of relativity."

In climbing as soon as you are moving something other than the climber (pulling gear, pulling a belayer off their stance, ripping a screamer) you are absorbing some of the fall force. If you then fall further you have a second fall that needs to be considered independently to the first, not as an addition to the forces generated in the original fall.

>Thanks also for the wikipedia reference where i found i did at least get>the FF calc correct; and as P noted, the elongation of the rope is not>relevant as the FF is the pre stress calculation. >>As i indicated in my note, my force calculations were an approximation,>i admit, for simplicity, and were given primarily for relative purposes>but also to show there are severe forces able to be generated even in 'small'>falls. >>Re the force calc; the energy in the fall would be mgh, this energy being>absorbed by the stretching rope and resulting in a force along the distance>it stretched,(which would be proportional to the length of rope deployed,>not the length of rope itself (as i wrongly calculated giving rise to>the mgh / r calc where it should have been mgh / (r x%elongation) (assuming>linear elongation in the foregoing)-sorry for the confusion).>
I think I've been misunderstood, whilst yes elongation has nothing to do with fall factor, it is a HUGE proportion of the force calculation ... but not: "mgh / (r x%elongation)"...

Jrc and Jacob make me realise how much I take my knowledge of simple physics for granted as it's related to climbing. I've observed over 10 years of climbing that engineers tend to be over-represented in climbing. I previously thought it was because of psychological parallels that attract this personality type to the activity, but now I realise it's just because they understand why they aren't going to die, whereas some others don't.

Jrc, you are making some very big and fundamental mistakes with units (force-Newtons, energy-Joules, etc) and prefixes (kilo=1000). For example, using your incorrect (static) equation for force m*g*FF = 80*10*2 = 1600N or 1.6kN (not 16kN). You could do a course in basic dynamics or just trust the basic guidlines climbers are taught will keep you safe.

For those not interested in maths there are two points relating to this that I think need clarifying, and as well as wishing the injured climbers a speedy recovery their response to clarifying here could be useful.

Shock loads (large forces over short periods of times) magnify anchor failure possibilities. "Stuff rips out when you yank on it".

Was the belayer clipped into the single cam belay with a static sling/daisy/lanyard? and were they either to the side or not tight below this?
If so this does produce greater loads it is always better to attach in with the climbing rope. A clove hitch is a great knot for this, easly adjustable without coming off the anchor.

Was the belay device a self locking device, like a gri gri eddie etc? If so the lack of slippage increases peak loading. especially once runners pull and the load is downwards onto the belayers harness.

If your climbing on gear really consider an ATC type belay device. If you end up with a fall directly onto the belay the slippage can burn hands but drastically reduces loading on an anchor.

While it's all very entertaining for us to hypothesise about fallfactors, this was almost certainly not a fall factor 2 situation.

First there was a nut placement that pulled in the fall

> I spotted a crack to my left and a foot up, which had a dried plant>growing out of it. I removed out the plant and scraped out the dirt and>got a shallow nut placed. It wasn't the greatest placement and I wasn't>happy with it but I left it in. I matched my left hand to the bomber pocket>my right was in and felt out with my right had to see if there was a carrot>I just wasn't seeing. My right hand came across what felt like a bomber>crimpy flake. I adjusted my weight to the right foot and loaded the right>hand to feel the wall with left hand.

Fairly safe to say that this nut was out to the side and probably not below his waist when the fall happened. So, more rope out than the climbers distance from the belay, Then the nut pulled in the fall, absorbing an unknown amount of kinetic energy. Odds are also, given the size of the ledges, that he bounced off the ledge to some extent. He also remarks "the force seemed to have a large horizontal component, probably from the nut placement out to the left." so it wasn't just a single massive downward impact on the belay. So, a bad impact but not factor 2

Rock_turtle also says :> unfortunately 3 point anchor was removed to walk along the ledge and>not reset when we walked back as we were still scouting the route. This>would be my biggest mistake I would say.

The frightening thing is that we don't actually know if that original anchor would have held the resultant fall if the cam failure was due to bad rock. 3 anchors in bad rock may be not much better than 1.

On 18/01/2013 hangdog wrote:> Pretty well everyone knows what we should do but who hasn't taken a short>cut at some point. So maybe some people need to get off the high horse>a bit and look at their own actions and think themselves lucky that nothing>serious happened as a result their own little shortcuts.

There's a fair bit of truth in this.

Like a lot of accidents this one seems to be the culmination of a number of smaller factors : unfamiliarity with the area leading to a bit of frustration, leading to a loss of focus, unfamiliarity with the rock leading to unexpectedly weak anchor placements and a fall.

On 22/01/2013 patto wrote:>On 22/01/2013 sliamese wrote:>>Sport climbers know how to give a dynamic belay(jumping) to give a soft>>catch.>>Trad climbers dont catch many falls, hence don't give a dynamic belay.>>!?! A dynamic belay for a FF2!? A "soft catch" FF2!>>Well I suppose in this case the belayer did give a dynamic belay, with>the obvious results.,,,

By letting rope slip through the belay device?

Or, clip a piece in the anchor, avoid the FF2, and also lower the impact by having the belayer launch towards the anchor. If something like a FF2 looks like a possibility, then the belayer could use a long safety so there is more rope between them and the top piece in the anchor.

Assuming the anchor holds in the upwards direction, if not, clipping the rope to the anchor may be a bad idea.